The invention relates to an apparatus for coupling a rotationally cylindrical part, in particular a shaft or a hub, in which a radially resilient bush is capable of being clamped to the cylindrical part by being radially acted upon by clamping elements; to this end, the clamping elements are exposed in turn to an axially operative spring assembly, in order to couple the cylindrical part to the bush or to a connection part joined to it. The release of the coupling is effected by means of a cylinder and piston arrangement that is actuated by a hydraulic pressure medium and acts upon the spring assembly counter to its force acting upon the clamping elements.
Various embodiments of such couplings are known. In German Patent 28 45 266, the object is fast blocking of a rod that passes axially through the coupling, while in the present case the coupling is intended primarily to bring about a releasable connection that is fixed against relative rotation. This connection fixed against relative rotation can be effected by means of conical tightening disks, which are combined into sets and are supported axially in the region of one face end, while on the other face end they are braced to the shaft or hub by axially acting spring elements. To release the coupling, the spring pressure must be suspended; this is effected hydraulically by means of a cylinder and piston arrangement. The terms "cylinder" and "piston" as used here should be understood here in the broadest sense. In other words, in the ensuing discussion they include any structural elements that form a chamber of variable volume for the pressure fluid and that are displaced relative to one another when pressure is imposed.